Lupus erythematosus and lupus nephritis: diagnosis

Laboratory diagnostics of lupus erythematosus and lupus nephritis

Laboratory studies with lupus nephritis are aimed at identifying signs of systemic lupus erythematosus and symptoms characterizing the activity of lupus nephritis and the state of kidney function.

Typical laboratory disorders include anemia, leukopenia with lymphopenia, thrombocytopenia, a sharp increase in ESR, hypergammaglobulinemia, the presence of LE cells, an antinuclear factor and antibodies to native DNA, hypocomplexemia (a decrease in the total hemolytic activity of the complement of CH-50, as well as of C3 and C4 fractions) .

The activity of lupus nephritis is judged by the severity of proteinuria, the presence of acute and / or nephrotic syndromes, the nature of urinary sediment, impaired renal function (an increase in creatinine concentration in the blood and a decrease in GFR).

Differential diagnosis of lupus erythematosus and lupus nephritis

With the expanded clinical picture of systemic lupus erythematosus, the diagnosis of lupus nephritis is practically not a problem. The diagnosis is established if there are any 4 or more of the 11 diagnostic criteria of the American Society of Rheumatologists (1997).

• Erythema of the face ("butterfly").
• Discoid rash.
• Photosensitivity.
• Halit, ulcers of the mouth.
• Non-erosive arthritis.
• Serositis (pleurisy, pericarditis).
• Renal damage (proteinuria more than 0.5 g / day and / or hematuria).
• Neurological disorders (cramps or psychosis).
• Hematologic disorders (hemolytic anemia, leukopenia and / or lymphopenia, thrombocytopenia).
• Increased titre of antibodies to DNA, the presence of antibodies to Sm-Ar, antiphospholipid antibodies (including IgG and IgM antibodies to cardiolipin or lupus anticoagulant).
• Positive antinuclear factor test.

Differential diagnosis of lupus erythematosus is carried out with other systemic diseases that occur with kidney damage: nodular polyarteritis, Schonlein-Henoch purpura, drug disease, autoimmune hepatitis, rheumatoid arthritis, myeloma, infections (subacute infective endocarditis, tuberculosis). With the erased systemic manifestations, it is necessary to differentiate lupus nephritis from chronic glomerulonephritis. In these cases, kidney biopsy can be invaluable, since histological examination of the material can reveal specific morphological signs of lupus nephritis.

• Nodular polyarteritis, in contrast to systemic lupus erythematosus, develops predominantly in men aged 30-50 years and proceeds with peripheral asymmetric polyneuritis, abdominalgia, coronary artery disease, leukocytosis. Renal damage in nodular polyarteritis is manifested by vasculitis of renal vessels with the development of persistent, often malignant arterial hypertension with a mildly expressed urinary syndrome (proteinuria, often in combination with microhematuria). Nephrotic syndrome is extremely rare.
• Kidney damage with Schönlein-Henoch purpura (hemorrhagic vasculitis) is often combined with the defeat of large joints, skin (characterized by recurrent symmetrical hemorrhagic rashes on the legs, buttocks, elbows), pain abdominal syndrome. Children and adolescents often get sick, often after a respiratory infection. Nephritis, as a rule, proceeds with an unusual for systemic lupus erythematosus machematuria and a high level of IgA in the blood.
• Close to lupus nephritis, a clinical picture can occur with rheumatoid arthritis with kidney damage, especially in the presence of other systemic manifestations (lymphadenopathy, anemia, lung damage). However, rheumatoid arthritis is characterized by a prolonged course of the disease with the development of persistent deformations of the joints, pronounced radiologic changes (erosive arthritis), high titers of the rheumatoid factor in the blood (in systemic lupus erythematosus, rheumatoid factor in the blood is not often and in low titres). With kidney biopsy, more than 30% of patients are diagnosed with amyloid, which is practically not detected with systemic lupus erythematosus.
• Sometimes it is difficult to differentiate lupus nephritis from kidney damage with drug disease, as well as in autoimmune hepatitis due to the numerous systemic manifestations inherent in these diseases as well as systemic lupus erythematosus.
  • The defeat of the kidney during drug disease often proceeds according to the type of interstitial nephritis, a characteristic feature of which, in addition to moderate urinary syndrome and acute renal failure of varying severity, tubular disorders, manifested primarily by a decrease in the relative density of urine. Morphological studies indicate a predominance of tubular changes and interstitium.
  • In autoimmune hepatitis, nephritis is rarely accompanied by massive proteinuria; for him the most characteristic tubulointerstitial component, often with pronounced tubular dysfunction. The decisive differential diagnostic value has signs of serious damage to the liver.
• Differential diagnosis of lupus nephritis is performed with myeloma nephropathy in women older than 40 years with sharply increased ESR, anemia, bone pain in combination with massive proteinuria without the formation of a nephrotic syndrome or progressive renal failure. Myeloma is confirmed by X-ray examination of flat bones, immunoelectrophoresis of blood and urine proteins, sternal puncture. A kidney biopsy with suspicion of myeloma is undesirable because of the risk of bleeding.
• For patients with systemic lupus erythematosus, differential diagnostics of lupus nephritis with infections requiring massive antibiotic therapy, especially with subacute infective endocarditis and tuberculosis with paraspecific reactions is extremely important.
  • Subacute infective endocarditis occurs with fever, leukocytosis, less frequent leukopenia, anemia, increased ESR, heart damage, and sometimes kidney failure. Nephritis is often of a hematuric nature, but nephrotic syndrome and even rapidly progressive glomerulonephritis may develop. An important differential diagnostic feature is the formation of aortic insufficiency, which is extremely rare in patients with lupus erythematosus in patients with systemic lupus erythematosus. An important differential diagnostic value is the "small" signs of subacute infective endocarditis: symptoms of tympanic sticks and watch glasses, a sign of Lukin-Liebman, a positive symptom of a pinch. In doubtful cases, blood sowing and trial treatment with high doses of antibacterial drugs are necessary.
  • It is equally important to exclude tuberculosis (which can join lupus nephritis after massive immunosuppressive therapy).

[1], [2], [3], [4], [5], [6], [7]